1. Field of the Invention
The present invention relates to a rifling angle calculating method, and more specifically, to a rifling angle calculating method capable of minimizing the maximum value of rifling force generated when a gun is fired, by expanding the rifling angle into a function of length of gun barrel.
2. Background of the Related Art
A rifling angle α is an angle expressing a shape y of rifling along the direction of length x of a gun barrel, which can be expressed in mathematical expression 1 shown below.
                              tan          ⁢                                          ⁢          α                =                              ⅆ            y                                ⅆ            x                                              [                  mathematical          ⁢                                          ⁢          expression          ⁢                                          ⁢          1                ]            
Conventionally, rifling is designed by stabilizing twist rate
      ⅆ    y        ⅆ    x  in the form of a linear or quadratic function. However, since rifling force generated by the designed rifling shows a maximum value locally, or a big rifling force appears at the time point when a projectile departs from the muzzle of a gun, the lifespan of the gun barrel or flight of the projectile may be negatively affected.
A method of expanding the rifling angle into a Fourier function has been proposed in order to improve the problems. However, if the rifling angle is expanded only into the Fourier function, convergence is guaranteed as the number of terms is increased, but it is disadvantageous in that boundary conditions cannot be satisfied. That is, since the convergence is processed only within the boundary conditions, there is no way to process the boundary conditions at the start and end points of the rifling angle, and thus the boundary conditions are processed only randomly.
If the rifling angle is expanded into a polynomial function, it is advantageous in that given boundary conditions may be faithfully satisfied, but the convergence is not guaranteed although the number of terms is increased.